The most intelligent and clear encyclical I've seen come from Rome... in my lifetime? Though we will not likely know exactly how much was written by Pope Benedict XVI, my estimate is 80% of it, the contrast is that unsurprisingly stark in thought and style. Without consciously looking for it, I suddenly found myself sensing a different tone and went back to look at several areas to find the sudden shift. Maybe not so noticeable to other readers but being a fan of the writing style of Joseph Ratzinger, I noticed. Concise and can be found online here: http://www.vatican.va/holy_father/francesco/encyclicals/documents/papa-francesco_20130629_enciclica-lumen-fidei_en.html